Blow molding has become a commercially important process for producing thermoplastic polymer containers, such as for example, biaxially oriented bottles. There are essentially two principle processes presently used commercially to produce blow molded biaxially oriented containers (e.g. bottles). The first process involves producing a hot preform (usually by an injection or extrusion process), transferring the hot preform usually by means of a mandrel to a blow mold, blowing the container in a closed mold by injecting pressurized air into the hot preform to expand the preform axially and circumfrentially against the mold cavity, and then removing the biaxially oriented container from the opened mold. This process usually employes a preform producing apparatus that is integral with or attached to the blow molding apparatus. In the second process a previously produced cold or cooled preform is reheated to a blowing temperature or temperature profile, the heated preform inserted into the cavity of a blow mold, the mold closed about the preform, the preform extended axially and simultaneously or subsequently expanded circumferentially to conform to the mold cavity and then the biaxially oriented container removed from the opened mold. Preform production in the second process is performed on apparatus separated from and often located at a distance from the blow molding apparatus. This second process is known and often referred to as a reheat blow process. In the blow molding process for producing thermoplastic polymer containers there may be employed an injection molded preform workpiece or alternatively a preform workpiece that is an extruded tube which has been closed at one end and shaped into an open neck configuration, usually threaded, at the other end. These injection molded or shaped extruded tube preforms are often test tube shaped having a curved closed end and a threaded open neck end. Such preforms are usually grasped at the open neck end and carried through the steps of the reheat blow molding process by means of a carrier apparatus whereupon the blown container is then released from the carrying device.
There is in conjunction with this invention employed in the blow molding process for producing thermoplastic polymer containers a step of heating a previously formed preform which is transported through the heating step by means of the same carrier used to carry the preform through the various other steps of the process.
The high production rate of the blow molding apparatus for economically producing thermoplastic polymer containers (e.g. 1000-2000 containers/hr) requires the very rapid positive loading of the carriers with the preforms. Such high loading rates in turn require that the preform carriers be rapidly and reliably activated for receiving the preforms. Where such activation of the preform carrier is performed mechanically the device which activates the carriers must have reliable, fast, positive action and high durability. Heretofore, mechanical apparatus for activation of the preform carriers for grasping and releasably retaining the preforms, to be conveyed through the blow molding process, have not been entirely satisfactory and have been susceptible to frequent breakdowns, malfunctions and failure to properly activate the preform carrier to receive the preform. Such malfunctions and failures result in down time for the blow molding machine and the loss of preforms and containers.
It is an object of this invention to rapidly, positively and reliably activate preform carriers for receiving and releasably retaining preforms in a blow molding apparatus for producing thermoplastic polymer containers. Another object of this invention is to provide a rapidly, positively and reliably operating durable apparatus for activating preform carriers for receiving and releasably retaining thermoplastic polymer preforms in a blow molding machine. A further object of this invention is to provide a blow molding machine having preform carriers for receiving and releasably retaining thermoplastic polymer preforms and a durable apparatus for rapidly, positively and reliably activating the preform carriers to receive and releasably retain the preform.
Other objects and advantages of this invention will become apparent from the following description and the claims.